# ungetc.m4 serial 2
dnl Copyright (C) 2009, 2010 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
dnl with or without modifications, as long as this notice is preserved.

AC_DEFUN_ONCE([gl_FUNC_UNGETC_WORKS],
[
  AC_REQUIRE([AC_PROG_CC])

  AC_CACHE_CHECK([whether ungetc works on arbitrary bytes],
    [gl_cv_func_ungetc_works],
    [AC_RUN_IFELSE([AC_LANG_PROGRAM([[
#include <stdio.h>
      ]], [FILE *f;
           if (!(f = fopen ("conftest.tmp", "w+"))) return 1;
           if (fputs ("abc", f) < 0) return 2;
           rewind (f);
           if (fgetc (f) != 'a') return 3;
           if (fgetc (f) != 'b') return 4;
           if (ungetc ('d', f) != 'd') return 5;
           if (ftell (f) != 1) return 6;
           if (fgetc (f) != 'd') return 7;
           if (ftell (f) != 2) return 8;
           if (fseek (f, 0, SEEK_CUR) != 0) return 9;
           if (ftell (f) != 2) return 10;
           if (fgetc (f) != 'c') return 11;
           fclose (f); remove ("conftest.tmp");])],
        [gl_cv_func_ungetc_works=yes], [gl_cv_func_ungetc_works=no],
        [gl_cv_func_ungetc_works='guessing no'])
    ])
  if test "$gl_cv_func_ungetc_works" != yes; then
    AC_DEFINE([FUNC_UNGETC_BROKEN], [1],
      [Define to 1 if ungetc is broken when used on arbitrary bytes.])
  fi
])
